Power transmission



July 20, 1943 R. A. sHARTLE POWER TRANSMISSION 'Filed Jan. 1o, 1941 2sheets-sheet 1 /f//wwwwww INVENTOR SHARTLE ROBERT A. BY

ATTORNEY K VIII.

4July 20, 1943. R. A. sHARTLE POWER TRANSMISSION 2 Sheets-Sheet 2 FiledJan. l0, 1941 ix m E INV EN TOR ROBERT A SHARTLE ATTORNEY Patented July20, 1943 POWER TRANSIVHSSION Robert A. Shartle, Rockford, Ill., assignerto Vickers Incorporated, Detroit, Mich., a corporation of MichiganApplication January 10,1941, serial No. 373,867 z Claimaj (ci. eso- 52)This invention relates to power transmissions, particularly to those ofthe type comprising, two

or more fluid pressure energy translating devices,

n retract the drill for the purpose of clearing the chips and coolingthe drill tipand to then return the drill to its work. There have beennumerous systems devised for controlling a hydrauthe parts in variouspositions at different `stages `of a complete cycle.

Referring now to Figure 1, a fixed displacement pump I `is adapted to bedriven by an electric lically actuated drill to produce step drilling,but Y heretofore all such systems have required specially designedcontrol apparatus making use of very `few, if any, of the standardhydraulic components now available on the market.

It is an object of the present invention to provide an improved controlsystem for step drilling which incorporates one ofthe standard hydrauliccontrol mechanisms which are used on a wide variety of machine tools forproducing a cycle of rapid advance, feed and rapid return movee ment andwhich, because of their wide eld of apof the drill a predetermined timeinterval after` the feed movement begins.

A further object is to provide an improved control system of thischaracter wherein the frictional dog is automatically reset during thefinal return movement of the drill carriage.

Further` objects and advantages of the present invention will beapparent from the following description, reference being had to theaccompanying drawings wherein a preferred form of the present inventionis clearly shown.

In the drawings:

Figure 1 is a diagrammatic view of a power transmission systemincorporating a preferred form "of the present invention.

Figures 2, 3 and 4 are schematic views of the hydraulic circuit and tripdog system showing motor i2 and has a suction conduit i4 connected witha tank i6. The delivery conduit I8 of the pump has the usual pressureresponsive relief valve 20 therein for bypassing oil to-tank through aconduit 22 whenever a predetermined pressure is exceeded in the conduitI8.`

The conduit i8 extends tothe pressure port of a control panel 24, thetank connection of which communicates with the conduit 22. The panel 24may be of well-known standard construction such, for example, as thatillustrated in the application of` Kenneth R. Herman et al., Serial No.155,652, filed July 26, 1937, for a Hydraulic feed control panel,nowIPatent No. 2,274,603.`

Briefly, such a panel .comprises a main control stem 28 having aplurality of lands thereon vfor controlling communication between thevarious passages within the panel to provide i'lve different owconditions; namely, a rapid advance, a coarse feed, a fine feed, a stopand a rapid reverse, as the stem is moved from right to left betweenthevarious positions illustrated.

`The stem'may be moved from the stop to the rapid advance position by asolenoid 28 acting. through a bell crank 30 to shift the stem to the lright whenever the solenoidis energized. Similarly, a solenoid 32 mayact through the ,bell crank 30 to shift the stem 26 completely totheleftto the rapid reverse position. l i

The panel also may include a pair of manually adjustable throttles 3land 33, one of which controls the fine feed and the otherof whichcontrols the coarse feed. A hydrostatic flow control valve 35` isarranged in series with the throttlesrto maintain a predeterminedpressure drop-"across them irrespective of variations inwork resistance.l 'I'he entire arrangement is such that,-in the rapid advance positionof stem 26, the delivery conduit I8 is connected `directly with aconduit 34 communicating with theupper end of a cylinder 36 the piston38 of which is connectedto actuate the drill carriage 40. In thisposition of the stem, the tank conduit `22 is also directly connectedwith a conduit l2 leading to the lower end of cylinder 36. I n

When the stem is shifted to coarse feed position, the pump deliveryremains connected to first throttle 3| is established between conduits42 and 22.

In the next position of the stem for producing fine feed, this path ismade to include the throttle 33 in addition to the throttle 3i, while inthe stop position the pressure and tank conduits I8 and 22. areconnected together to bypass the pump delivery. With the stem 26 shiftedto rapid return position, conduit I 8 is directly connected with conduit42, and conduit 34 is directly connected with conduit 22.

'Ihe conduit 42 may include a foot valve 39 of known construction suchas illustrated in the Herman Patent No. 2,200,824 including aselfcontained check valve 4I for free now from the panel to the cylinderand a pressure-responsive, back-pressure valve 43 arranged to preventbackow from the cylinder except at a pressure above that produced by thegravity load on piston 38.

Although the standard control panel includes provision for both coarseand fine feed rates, only one of the feed rates is necessary for stepdrilling so that the other feed position of stem 26 is not utilized inthe mechanism hereafter described.

For the purpose of controlling the position of stem 26, the drillcarriage 40 carries an upstanding bar 44 on which various trip dogs aremounted for actuating the stem 26 directly and for actuating certainlimit switches which control the energization of solenoids 28 and 32.46, rigidly but adjustably secured to the bar 44, is arranged to actuatea limit switch 48 at the lower end of the stroke of carriage 40. Theswitch 48 has two normally open circuits and one normally closedcircuit.

A dog 50. rigidly but adjustably secured to the bar 44, has a portion 52arranged to contact a single-circuit, normally-open, limit switch 54just before the carriage 40 reaches the upper limit of its stroke. Asecond portion 56 forms a hook cam for pulling the stem 26 to the right.from its rapid return position to its stop position as the carriagelreaches the upper end of its stroke.

A cam bar 58 is also carried by the bar 44 for the purpose of resettinga sop pin 60 which is arranged to be projected to the right by asolenoid 62 whenever the latter is energized for a purpose later to bedescribed.

Finally, the bar 44 carries a dog 64 which is slidably mounted on thebar with frlctional engagement sufiicient to prevent relative movementbetween the dog 64 and the bar 44 when the dog passes the stem 26 butinsuiiicient to stop movement of the carriage when the dog strikes apositive stop. Such a stop is formed by a limit switch 66 of thesingle-circuit, normally-open type which is arranged to be contacted byan adjustable screw 68 carried by the dog 64 just after the lattershifts the stem 26 from rapid advance position to feed position.

For the purpose of controlling the energization of solenoids 28 and 32,an electric circuit is provided which includes a two-circuit,normallyopen, manual starting switch 10, the upper circuit of which,when closed, connec-ts between one side of a suitable power lineindicated by L1 and through a conductor 14 to the actuating coil of aholding relay 12. The other side of the coil is connected to the otherside of the line indicated at L2. The lower circuit of switchI isarranged, when closed, to connect line L1 to a conductor 16 leading tothe solenoid 28, the other side of which is connected to line L2. Abranch conductor 18 extends through the normally-open controlledcontacts of relay 12 and through limit vswitch 54 Thus, a dog to lineL1, thus forming, when closed, a shunt around the lower circuit ofswitch 10.

The holding circuit of relay 12 extends from one side of the coilthereof through the holding contacts and through a conductor to thenormally-closed contacts of a two-circuit, emergency-return switch 82.This holding circuit continues through a conductor 84 and through thenormally-closed contacts of limit switch 48 to the line L1. The leftmostnormally-open contacts of limit switch 48 are adapted to close a circuitextending from line L1 through a conductor 86 -to the solenoid 32, theother side of which is connected to line L2. A branch 88 extends fromthe normally-open contacts of reverse switch 82 to the conductor 86 andis in parallel with the limit switch 48. The middle contacts of limitswitch 46 close a circuit from line Ll through conductor 90 to thesolenoid 62, the other side of which is connected to line L.

'I'he limit switch 66 controls a circuit extending between line L2 andthe initiating coil of a time delay relay 92 by a conductor 94. Theoutput circuit of relay 92 connects by a conductor 86 with the conductor86. A connection 98 provides a common return for both circuits 94 and 98at the relay 92.

In operation, with the pump I8 running and with the parts in the stoppedposition illustrated in Figure l, the pump delivery is bypassed throughthe panel 24, and the drill .carriage 48 is supported on the column ofoil beneath piston 38 which is prevented from escaping by means of thefoot valve 39.

When it is desired to start a cycle of step drilling, the startingswitch 18 may be depressed which energizes the holding relay 12, theholding circuit of which is then completed through conductor 80, switch82, cqpductor 84 and switch 48 to form a shunt around the upper contactsof switch 10. The lower contacts of switch 18 energize the solenoid 26through conductor 16, thus shifting the stem 26 into rapid advanceposition. The pump delivery is now directed from conduit I8 throughpanel 24 directly to conduit 34 and the head end of cylinder 36.Pressure immediately builds up suiiicient to overcome the setting offoot valve 38, permitting oil to discharge from the lower end ofcylinder 36 through conduit 42 which is in direct communication throughthe panel 24 with conduit 22.

The drill carriage accordingly approaches at full speed until a point isreached where the drills are about to engage the work. When this pointis reached, dog 64 contacts stem 26, shifting it to the left into feedposition, thus throwing the hydrostatic valve and throttle into theoutlet cir- .cuit between conduit 42 and tank conduit 22. The carriage40 is accordingly slowed down to the feed rate, and the excess pumpdelivery is bypassed to tank through the relief valve 28.

Immediately after shifting the stem 26 to feed position, the stop screw68 contacts limit switch 66, and, after closing the same, the dog 64 canno longer descend with the carriage. Accordingly, the bar 44 is pulledthrough the dog 64 overcoming the frictional engagement therebetween. Atthe same time the closure of switch 66 initiated operation of the timedelay relay 82, and, after thepredetermined time interval for which therelay is set, it closes the circuit between line connection 98 andconductor 96 which accordingly energizes solenoid 32 through conductor86. When this occurs, the stem 26 is shifted completely to the left intothe rapid returnposition, causing the slide 40 to be retracted at fullspeed. It will be noted that. when this rapid return movement starts,the dog 64 has taken up a new position on the rod 44 indicated by dottedlines at 64a.

Just before the slide reaches the upper limit of its travel, cam portion52 of dog 50 closes limit switch 54 to energize solenoid 28 throughconductor 18, relay 12 and conductor 16. Accordingly, the stem 26 isagain shifted completely to the right to rapid advance position, and thecarriage again advances at full speed. This time it advances furtherthan it did on the rst rapid advance stroke or, in other words, untildog 64 in its new position engages stem 26 to shift the same to its feedposition. From this point on, the same actions which have been describedabove occur, and, after a, predetermined interval,

`.At this time the dog 64 has taken up a third position on the bar 44indicated in dotted lines at 64b.

This cycle of advancing and returning movement is continuous until thehole is drilled to its full depth at which time the dog 46 engages thelimit switch 48 which simultaneously accomplishes three functions.First, it opens the holding circuit 80-82--84 of relay 12, permitting'the latter to drop and form a break in the conductor 18, thus disablinglimit switch 54 so that dog 52 will not start an advance stroke as thecarriage 46 returns to its uppermost position. The second thing whichlimit switch 48 accomplishes is to energize solenoid 62 throughconductor 90. thus projecting the stop pin 60 into the path of dog 64.as shown in Figure 4. Thirdly, the limit switch 48 energizes solenoid 32through conductor 86, thus shifting stem 26 to rapid return position andcausing the carriage 46 to be retracted.

During the upward travel of carriage 40, dog

` i 64 will engage stop pin 66 and be prevented thereby from returningupwardly with the bar 44. In this way the dog 64 is reset to itsoriginal position on the bar. When it has reached this position, the cam58 engages a transverse pin on the stop pin 66 and gradually cams thelatter back to the left so that the dog 64 can thereafter pass the pin60 until the parts have returned to their i form, it is to be understoodthat other forms might be adopted. all coming within the scopestandardized construction normally used for operating a drill carriagethrough a cycle of rapid advance, feed, rapid return and stop-movements,and having a single control member constituting the sole selecting meansfor said movements, of a dog for shifting the control member to changefrom rapid advance to feed carried by the carriage in yieldingfrictional relation thereto, means forming a positive stop to preventfurther movement of the dog while the carriage advances in feedingmovement, time delay means initiated in operation when the dog isstopped for shifting the controller to cause rapid return after apredetermined time interval, means controlled by the carriage at apredetermined point in its return movement for shifting the controllerto cause rapid advance until the dog in its new position relative to thecarriage shifts the controller to again cause feeding movement, andmeans controlled by the carriage after advancing to a predeterminedpoint for immediately causing rapid return independently of the timedelay means.

2. In a hydraulic power transmission system for step drilling thecombination with a pressure source, a fluid motor and a flow controllerof standardized construction normally used for operating a drillcarriage through a cycle of rapid advance, feed, rapid return and stopmovements, and having a single control member constituting the soleselecting means for said movements, of a dog for shifting the controlmember to change from rapid advance to feed carried by the carriage inyielding frictional relation thereto, means forming a positive stop toprevent further movement of the dog while the carriage advances infeeding movement, time delay means initiated in operation when the dogis stopped for shifting the controller to cause rapid return after apredetermined time interval, means controlled by the carriage at apredetermined point in its return movement for shifting the controllerto cause rapid advance until the dog in its new position relative to thecan'iage shifts the controller to again cause feeding movement, andmeans controlled by the carriage after advancing to a predeterminedpoint for immediately causing rapid return independently of the timedelay means and being arranged to disable the carriage-controlled meanswhereby the carriage is prevented from readvancing.

ROBERT A. SHAR'ILE.

